Antibody Targeting

Targeting requires the targeting agent to have good selectivity in order to achieve efficient targeting. Antibodies bind to their targets with high specificity and binding efficiency and this makes them ideal candidates for targeted drug delivery. However, this requires the identification of surface protein markers that are unique to the tumor. Fortunately for many types of cancer specific antigens has been identified. For instance, prostate cancer therapeutics delivery can utilize prostate specific antigen (PSA) and prostate specific membrane antigen (PSMA) as their targets.

A major difference between antibody targeting and antibody therapy is in the requirement of the Fc region. The Fc region of antibodies is important for binding to phagocytotic cells such as the macrophages to activate them. Antibody therapies require “human” forms of the Fc region in order to properly interact with the body’s immune system and this is often difficult to achieve. However, using antibody to selectively deliver drugs circumvents this problem. In this case, the therapy relies on the drugs to kill cancer cells, not the body’s immune system. Therefore, no activation of the immune system is required and the Fc region is not needed. This greatly simplifies the synthesis of the antibody fragments.

Antibodies has been conjugated to many different molecules to create targeted delivery systems including cytotoxic molecules, radioactive elements and carriers such as liposomes.